Reasons to add sync flags to Bitcoin

The concept of selfish mining of sync flags has been introduced, where flags will be mined selfishly and not published until the advantage gained from withholding is less than the mining reward. This act may result in killing the decentralization features as big miners would be the only ones capable of engaging in selfish-mine flags. Furthermore, this could encourage collusion among miners, leading to a situation where they would only ship the flag to the miners they have business with, at the expense of loss of flag revenue. This practice would give their in-group a significant advantage in main-chain mining.